Wikimedia Cloud Services team/EnhancementProposals/Toolforge jobs

From Wikitech
Tracked in Phabricator
Task T285944
This enhancement proposal was eventually accepted. The content of this page was relocated to Portal:Toolforge/Admin/Kubernetes/Jobs framework


This page contains information on a potential design to support grid-like jobs on Toolforge kubernetes, the end goal being to help in GridEngine deprecation.

Proposal

This proposal consist on introducing a framework called Toolforge Jobs Framework (or TJF). It is basically a new API to ease end user interaction with Toolforge jobs in the kubernetes cluster. The new API should abstract away most of the k8s gory details for configuring, removing, managing and reading status on jobs. The abstraction approach is similar to what is being done with Toolforge webservices (we have the webservice command there), but with a new approach that consist on decoupling the software into 2 components: an API service and a command line interface.

The framework consists precisely in these two components.

The API is freely usable within Toolforge, both bastion servers and kubernetes pods. This means that a running job can interact with the Toolforge jobs API and CRUD other jobs.

There are no plans to introduce backwards support for GridEngine in TJF, given the ultimate goal is to deprecate the old grid.

The two components approach

The TJF is composed of 2 components:

  • toolforge-jobs-api --- runs inside the k8s cluster as a webservice. Offers the REST API that in turn interacts with the k8s API native objects: CronJob, Job and ReplicationController.
  • toolforge-jobs-cli --- command line interface to interact with the toolforge-job-api service. Typically used by end users in Toolforge bastions.

By splitting the software into two components, and introducing an stable API, we aim to reduce maintenance burden by not needing to rebuild all Toolforge docker containers every time we change some internal mechanism (which is the case of the tools-webservice package).

Also, the new REST API can be used by any user inside Toolforge. We open the door to enable a simplified programmatic usage of this new kubernetes jobs feature, which can be a nice incentive for users to migrate away from the grid.

k8s abstraction that matches GridEngine experience

We would like to support a similar experience to what users are used to in GridEngine. Given the feature mapping table below, it should be possible in Kubernetes by using the following mechanisms:

  • Job. This object is the basic definition of a workload in the k8s cluster that makes it run a given task and ensure it finished as expected.
  • CronJob. This object support cron-like scheduling of child Jobs objects.
  • ReplicationController. This object is used to ensure a given Job is present. Used to control execution of continuous tasks, a feature not supported natively in the Job object.

Auth

Tracked in Phabricator
Task T274139

To ensure that Toolforge users only manage their own jobs, TJF will use kubernetes certificates for client authentication. These x509 certificates are automatically managed by maintain-kubeusers, and live in each user home directory: 

toolsbeta.test@toolsbeta-sgebastion-04:~$ egrep client-certificate\|client-key .kube/config
    client-certificate: /data/project/test/.toolskube/client.crt
    client-key: /data/project/test/.toolskube/client.key
toolsbeta.test@toolsbeta-sgebastion-04:~$ head -1 /data/project/test/.toolskube/client.crt
-----BEGIN CERTIFICATE-----
toolsbeta.test@toolsbeta-sgebastion-04:~$ head -1 /data/project/test/.toolskube/client.key
-----BEGIN RSA PRIVATE KEY-----

In the current Toolforge webservice setup, TLS termination is done at the nginx front proxy. The front proxy talks to the backends using plain HTTP, with no simple options for relaying or forwarding the original client TLS certs. We would need to introduce modifications to the front proxy to accept client TLS certificates, so instead we decided to run a parallel ingress.

The toolforge-jobs-api component needs to know the client certificate CommonName. With this information, toolforge-jobs-api will be able to supplant the user by reading again the x509 certificates from the user home, and use them to interact with the kubernetes API. This is effectively a TLS proxy that reuses the original certificate.

This results in two types of connections, as shown in the diagram above:

  • connection type 1: an user contacts toolforge-jobs-api using k8s client TLS certs from its home directory. The TLS connection is established to the ingress-ngnx-jobs, which has the client-side TLS termination. This can happen from a Toolforge bastion, or from a Job already running inside kubernetes. The connection can be made either using toolforge-jobs-cli or directly contacting toolforge-jobs-api programmatically by other methods.
  • connection type 2: once the CommonName of the original request certificate is validated, toolforge-jobs-api can load the same k8s client TLS certificate from the user home, and supplant the user to contact the k8s API. For this to be possible, the toolforge-jobs-api component needs permissions for every user home directory, pretty much like maintain-kubeusers has.

This setup is possible because the x509 certificates are maintained by the maintain-kubeusers component, and because toolforge-jobs-api runs inside the kubernetes cluster itself and therefore can be configured with enough permissions to read each users home.

More or other authentication mechanisms can be introduced in the future as we detect new use cases.

The Toolforge front proxy exists today basically for webservices running in the grid. Once the grid is fully deprecated and we no longer need the front proxy, we could re-evaluate this whole situation and simplify it.

Not using the framework

Advanced Toolforge users that know how to interact with a Kubernetes API can still use it directly (like for webservices). Using the new TJF is optional and is provided just as a convenient facility for Toolforge users.

The containers problem

We have custom-built containers for Toolforge webservices. Containers for the most common web development frameworks and language runtimes. Each container don't include every and each language and framework in the universe for practical reasons.

However, users can currently schedule jobs in GridEngine using any language, library or framework installed in our Debian bastions. They can write a script that combines calls to Python, PHP and Perl. We would need to think and develop a container solution that enables job users with the appropriate runtimes.

For the few first iterations of this project it can suffice to make pywikibot available. We can work later on to discover more useful runtimes.

Implementation details

TODO: Arturo would like to use Python3 to build TJF, using flask-restful https://flask-restful.readthedocs.io

Checking client TLS certs: https://www.ajg.id.au/2018/01/01/mutual-tls-with-python-flask-and-werkzeug/

dcaro: Might be interesting to use https://pypi.org/project/flask-swagger/ also (specially if the api is open)

hieu: check https://fastapi.tiangolo.com/

timeline

Proposed timeline for implementation, development and feature rollout.

  • FY20/21 Q3: Design & proposal. Basic TJF source code bootstrap.
  • FY20/21 Q4: A minimal TJF is developed. Select a few beta testers and early adopters.
  • FY21/22 Q1: Announce to the community new framework availability, work with users to migrate to it.
  • FY21/22 Q2: Closer to grid deprecation? <3

about logs

If left unattended, logs produced by jobs can easily hammer and bring down our etcd clusters We should come with a solution to strictly restrict logging, and redirect them to each user NFS home directory.

Some potential ideas on how to do that at kubernetes level: https://kubernetes.io/docs/concepts/cluster-administration/logging/

To be clear, this means that logs produced by jobs should not be made available using kubectl logs because that means the stderr/stdout of the pod is being RW in the etcd cluster.

URL

Relevant URLs in the Toolforge project:

Relevant URLs in the Toolsbeta project:

  • TBD

Feature mapping

Each currently supported use case in the grid should have an equivalent feature in kubernetes. The table below should help map each one.

Additionally, the table shows how each feature would map to the TJF.

Toolforge jobs feature mapping table
Feature GridEngine Kubernetes toolforge-jobs-cli toolforge-jobs-api
simple one-off job launch jsub native Job API support toolforge-jobs run <cmd> --type <container> POST /api/v1/run/
get single job status qstat kubectl describe job toolforge-jobs show <id> GET /api/v1/show/{id}/
get all jobs status qstat kubectl + some scripting toolforge-jobs list GET /api/v1/list/
delete job jstop kubectl delete toolforge-jobs delete <id> DELETE /api/v1/delete/{id}/
delete all jobs some scripting kubectl delete toolforge-jobs flush DELETE /api/v1/flush/
scheduled jobs crontab + jsub native CronJob API support toolforge-jobs run <cmd> --type <container> --schedule <sched> POST /api/v1/run/
continuous job launch (bot, daemon) jstart native ReplicationController API support toolforge-jobs run <cmd> --type <container> --continuous POST /api/v1/run/
concurrency limits 16 running + 34 scheduled TBD. several potential mechanisms TBD TBD
get stderr / stdout of a job files in the NFS directory files in the NFS directory No initial support No initial API support
request additional mem jsub -mem TBD. we may not need this TBD TBD
sync run jsub -sync y TBD. no native support toolforge-jobs run <cmd> --type <container> --wait POST /api/v1/run/ + GET /api/v1/show/{id}/
making sure a job only runs once jsub -once native Job API support toolforge-jobs run <cmd> --type <container> POST /api/v1/run/
listing available containers No support / not required Similar to what we do on tools-webservices toolforge-jobs containers GET /api/v1/containers/

API docs

This section contains concrete details for the API that TJF introduces.

POST /api/v1/run/

Creates a new job in the kubernetes cluster.

POST /api/v1/run/ details
The following content has been placed in a collapsed box for improved usability.


Request parameters
name datatype required comment
name string yes Name identification for the new job
cmd string yes Job command line to execute, including arguments
type string yes Job container type
schedule string optional If present, job will be scheduled. String is cron syntax, like */1 * * * *. Mutually exclusive with continuous.
continuous boolean optional If true, job will be persistent. Mutually exclusive with schedule.

Example request data: 

{
  "name": "myjob",
  "cmd": "./myscript.py --once",
  "type": "toolforge-buster-sssd",
  "schedule": "*/1 * * * *"
}
The above content has been placed in a collapsed box for improved usability.

GET /api/v1/show/{name}/

Shows information about a job in the kubernetes cluster.

GET /api/v1/show/{name}/ details
The following content has been placed in a collapsed box for improved usability.


Request parameters
name datatype required comment
name string yes Job name identification
Response parameters
name datatype comment
name string Job name identification
cmd string Job command line, including arguments
type string Job container type
schedule string Job schedule string in cron syntax, like */1 * * * *
continuous boolean True if job is persistent
state string Job current state

Example response JSON data: 

{
  "name": "myjob",
  "cmd": "./myscript.py --once",
  "type": "python",
  "continuous": false,
  "state"; "finished"
}
The above content has been placed in a collapsed box for improved usability.

DELETE /api/v1/delete/{name}

Delete a job in the kubernetes cluster.

DELETE /api/v1/delete/{name} details
The following content has been placed in a collapsed box for improved usability.
Request parameters
name datatype required comment
name string yes Job name identification
The above content has been placed in a collapsed box for improved usability.

GET /api/v1/list/

Shows information about all user jobs in the kubernetes cluster.

GET /api/v1/list/ details
The following content has been placed in a collapsed box for improved usability.


There are no request parameters.

Response parameters (list)
name datatype comment
name string Job name identification
cmd string Job command line, including arguments
type string Job container type
schedule string Job schedule string in cron syntax, like */1 * * * *
continuous boolean True if job is persistent
state string Job current state

Example response JSON data: 

[
  {
    "name": "myjob",
    "cmd": "./myscript.py --once",
    "type": "toolforge-buster-sssd",
    "continuous": false,
    "state": "finished"
  },
  {
    "name": "myotherjob",
    "cmd": "./myotherscript.py --once",
    "type": "toolforge-buster-sssd",
    "schedule": "*/1 * * * *",
    "state": "running"
  }
]
The above content has been placed in a collapsed box for improved usability.

DELETE /api/v1/flush/

Delete all user jobs in the kubernetes cluster.

DELETE /api/v1/flush/ details
The following content has been placed in a collapsed box for improved usability.

There are no request parameters.

The above content has been placed in a collapsed box for improved usability.

GET /api/v1/containers/

Shows information about all containers available for jobs in the kubernetes cluster.

GET /api/v1/containers/ details
The following content has been placed in a collapsed box for improved usability.


There are no request parameters.

Response parameters (list)
name datatype comment
name string container shortname
type string container URL

Example response JSON data: 

[
    {
        "name": "tf-buster",
        "type": "docker-registry.tools.wmflabs.org/toolforge-buster-sssd:latest"
    },
    {
        "name": "tf-buster-std",
        "type": "docker-registry.tools.wmflabs.org/toolforge-buster-standalone:latest"
    }
]
The above content has been placed in a collapsed box for improved usability.

Ingress & TLS

There are 2 nginx-ingress deployments in parallel in the k8s cluster:

  • the general one for all toolforge tools, in the ingress-nginx namespace, untouched by this project
  • the jobs-specific one, in the ingress-nginx-jobs namespace.

The jobs-specific one is able to read TLS client certificates and pass the ssl-client-subject-dn HTTP header to the pod running the toolforge-jobs-api webservice. With this information toolforge-jobs-api can load again the client cert when talking to the k8s API on behalf of the original user.

The way this whole ingress /TLS setup works is as follows:

  • To reach the ingress-nginx-jobs ingress, there is a FQDN jobs.svc.toolsbeta.eqiad1.wikimedia.cloud that points to the k8s haproxy VIP address.
  • The haproxy system listens on 30001/TCP for this jobs-specific ingress (and in 30000/TCP for the general one).
  • The haproxy daemon reaches k8s ingress nodes on 30001/TCP (the ingress-nginx-jobs-svc so traffic both internal and external to the cluster can reach the nginx proxy.
  • The ingress-nginx-jobs is configured to only load 1 Ingress object, which is the one defined for the toolforge-jobs-api.
  • The Ingress object instructs ingress-nginx-jobs to enable client TLS by using the annotation nginx.ingress.kubernetes.io/auth-tls-verify-client: on and nginx.ingress.kubernetes.io/auth-tls-pass-certificate-to-upstream: "true".
  • Client TLS certs are verified against the kubernetes CA, which should be configured in the nginx.ingress.kubernetes.io/auth-tls-secret: "default/ca-secret" annotation of the Ingress object.
  • Once the TLS certs are verified the proxy injects the HTTP header ssl-client-subject-dn to toolforge-jobs-api, which contains the CN= information of the original user.
  • With the ssl-client-subject-dn header, toolforge-jobs-api can load again the client certificate from the original user home on NFS and in turn contact the k8s API using them.

In order for the 2 nginx-ingress deployments on the cluster to ignore each other Ingress objects, we need a few additional bits.

in kubernetes 1.17

Per upstream docs we need to pay attention to the --ingress-class nginx command line flag.

  • the general ingress, using the default value (unset), which means it will process every ingress with the kubernetes.io/ingress.class: "nginx" annotation or with no annotation at all.
  • the jobs ingress, using --ingress-class=jobs, which will handle every ingress with the kubernetes.io/ingress.class: "jobs" annotation (there should be just one).

in kubernetes 1.18

Per the release notes, the kubernetes.io/ingress.class annotation is deprecated, and the IngressClass resource should be used instead. The Ingress object should use the new ingressClassName field.

Development

Some random stuff that Arturo has written here.

notes on k8s objects

Example workflow using the k8s API with a Job object
The following content has been placed in a collapsed box for improved usability. 
tools.arturo-test-tool@tools-sgebastion-08:~$ kubectl delete job arturo-test-job ; kubectl apply -f job.yaml 
job.batch "arturo-test-job" deleted
job.batch/arturo-test-job created
tools.arturo-test-tool@tools-sgebastion-08:~$ cat job.yaml 
apiVersion: batch/v1
kind: Job
metadata:
  name: arturo-test-job
spec:
  backoffLimit: 3
  template:
    spec:
      containers:
      - name: arturo-test
        image: docker-registry.tools.wmflabs.org/toolforge-buster-sssd:latest
        workingDir: /data/project/arturo-test-tool/
        command:
          - ./arturo-test-script.sh
        env:
        - name: HOME
          value: /data/project/arturo-test-tool
        volumeMounts:
        - mountPath: /data/project
          name: home
      restartPolicy: Never
      volumes:
      - hostPath:
          path: /data/project
          type: Directory
        name: home
tools.arturo-test-tool@tools-sgebastion-08:~$ kubectl get jobs
NAME              COMPLETIONS   DURATION   AGE
arturo-test-job   1/1           9s         88s
tools.arturo-test-tool@tools-sgebastion-08:~$ kubectl get pods
NAME                    READY   STATUS      RESTARTS   AGE
arturo-test-job-9lzkc   0/1     Completed   0          94s
tools.arturo-test-tool@tools-sgebastion-08:~$ kubectl logs job/arturo-test-job
arturo test script
Done sleeping
The above content has been placed in a collapsed box for improved usability.
Example workflow using the k8s API with a CronJob object
The following content has been placed in a collapsed box for improved usability. 
toolsbeta.test@toolsbeta-sgebastion-04:~$ cat cronjob.yaml 
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: test-cronjob
spec:
  schedule: "*/1 * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: test-job
            image: docker-registry.tools.wmflabs.org/toolforge-buster-sssd:latest
            workingDir: /data/project/test/
            command:
              - ./test-script.sh
            env:
            - name: HOME
              value: /data/project/test     
            volumeMounts:
            - mountPath: /data/project
              name: home
          restartPolicy: Never
          volumes:
          - hostPath:
              path: /data/project
              type: Directory
            name: home
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl apply -f cronjob.yaml 
cronjob.batch/test-cronjob created
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl get cronjob
NAME           SCHEDULE      SUSPEND   ACTIVE   LAST SCHEDULE   AGE
test-cronjob   */1 * * * *   False     0        <none>          5s
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl describe cronjob test-cronjob
Name:                          test-cronjob
Namespace:                     tool-test
[..]
Schedule:                      */1 * * * *
[..]
Events:
  Type    Reason            Age    From                Message
  ----    ------            ----   ----                -------
  Normal  SuccessfulCreate  4m29s  cronjob-controller  Created job test-cronjob-1611663900
  Normal  SawCompletedJob   4m19s  cronjob-controller  Saw completed job: test-cronjob-1611663900, status: Complete
  Normal  SuccessfulCreate  3m29s  cronjob-controller  Created job test-cronjob-1611663960
  Normal  SawCompletedJob   3m19s  cronjob-controller  Saw completed job: test-cronjob-1611663960, status: Complete
  Normal  SuccessfulCreate  2m29s  cronjob-controller  Created job test-cronjob-1611664020
  Normal  SawCompletedJob   2m19s  cronjob-controller  Saw completed job: test-cronjob-1611664020, status: Complete
  Normal  SuccessfulCreate  89s    cronjob-controller  Created job test-cronjob-1611664080
  Normal  SawCompletedJob   78s    cronjob-controller  Saw completed job: test-cronjob-1611664080, status: Complete
  Normal  SuccessfulDelete  78s    cronjob-controller  Deleted job test-cronjob-1611663900
  Normal  SuccessfulCreate  38s    cronjob-controller  Created job test-cronjob-1611664140
  Normal  SawCompletedJob   28s    cronjob-controller  Saw completed job: test-cronjob-1611664140, status: Complete
  Normal  SuccessfulDelete  28s    cronjob-controller  Deleted job test-cronjob-1611663960
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl get jobs
NAME                      COMPLETIONS   DURATION   AGE
test-cronjob-1611664020   1/1           2s         2m33s
test-cronjob-1611664080   1/1           3s         93s
test-cronjob-1611664140   1/1           2s         42s
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl delete cronjob/test-cronjob
cronjob.batch "test-cronjob" deleted
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl get jobs
No resources found in tool-test namespace.
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl get cronjobs
No resources found in tool-test namespace.
The above content has been placed in a collapsed box for improved usability.
Example workflow using the k8s API with a ReplicationController object
The following content has been placed in a collapsed box for improved usability. 
toolsbeta.test@toolsbeta-sgebastion-04:~$ cat replicationcontroller.yaml
apiVersion: v1
kind: ReplicationController
metadata:
  name: test-continous-job
spec:
  replicas: 1
  selector:
    app: test-job
  template:
    metadata:
      name: test-job
      labels:
        app: test-job
    spec:
      containers:
      - name: test-job
        image: docker-registry.tools.wmflabs.org/toolforge-buster-sssd:latest
        workingDir: /data/project/test/
        command:
          - ./test-script-whiletrue.sh
        env:
        - name: HOME
          value: /data/project/test
        volumeMounts:
        - mountPath: /data/project
          name: home
      restartPolicy: Always
      volumes:
      - hostPath:
          path: /data/project
          type: Directory
        name: home
toolsbeta.test@toolsbeta-sgebastion-04:~$ cat test-script-whiletrue.sh 
#!/bin/bash
while true ; do
  echo "INFO: running test script"
  date
  sleep 5
done
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl apply -f replicationcontroller.yaml 
replicationcontroller/test-continous-job created
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl get replicationcontroller
NAME                 DESIRED   CURRENT   READY   AGE
test-continous-job   1         1         1       12s
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl get pods
NAME                           READY   STATUS    RESTARTS   AGE
test-continous-job-m5sxh       1/1     Running   0          17s
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl logs test-continous-job-m5sxh
INFO: running test script
Tue 26 Jan 2021 12:38:02 PM UTC
INFO: running test script
Tue 26 Jan 2021 12:38:07 PM UTC
INFO: running test script
Tue 26 Jan 2021 12:38:12 PM UTC
INFO: running test script
Tue 26 Jan 2021 12:38:17 PM UTC
INFO: running test script
Tue 26 Jan 2021 12:38:22 PM UTC
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl delete pod test-continous-job-m5sxh
pod "test-continous-job-m5sxh" deleted
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl get pods
NAME                           READY   STATUS    RESTARTS   AGE
test-continous-job-95n98       1/1     Running   0          64s
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl describe replicationcontroller/test-continous-job
Name:         test-continous-job
Namespace:    tool-test
[..]
Events:
  Type    Reason            Age   From                    Message
  ----    ------            ----  ----                    -------
  Normal  SuccessfulCreate  111s  replication-controller  Created pod: test-continous-job-m5sxh
  Normal  SuccessfulCreate  77s   replication-controller  Created pod: test-continous-job-95n98
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl delete replicationcontroller test-continous-job
replicationcontroller "test-continous-job" deleted
toolsbeta.test@toolsbeta-sgebastion-04:~$ kubectl get pods
NAME                           READY   STATUS        RESTARTS   AGE
test-continous-job-95n98       1/1     Terminating   0          3m40s
The above content has been placed in a collapsed box for improved usability.

development environment

The development environment is somewhat non trivial to set up. Given that TJF operates in a way similar to maintain-kubeusers, you will need a local kubernetes clusters (using minikube) to be able to emulate the Toolforge environment.

TODO: add more information here.

source code

Gerrit repositories:

See also

Internal documents:

Some upstream kubernetes documentation pointers:

Related components:

Retrieved from "https://wikitech.wikimedia.org/w/index.php?title=Wikimedia_Cloud_Services_team/EnhancementProposals/Toolforge_jobs&oldid=1984929"